Tow band

ABSTRACT

A CONTINUOUS FILAMENT POLYESTER TOW BAND PRODUCED FROM A PLURALITY OF SUBTOWS AND CHARACTERIZED BY A LIMITED AND CONTROLLED DEGREE OF INTERMINGLING OF FILAMENTS.

April 4, 1912 N, Y 3,654,055

TOW BAND Filed Sept. 8, 1970 I 3 Sheets-Sheet 1 April 4, 1972 v J. N.GRAY TOW BAND Filed Sept. 8, 1970 s Sheets-Sheet 2 April 4, 1972 J. N.GRAY TOW BAND 3 Sheets-Sheet 5 Filed Sept. 8, 1970 United States PatentOffice 3,654,055 Patented Apr. 4, 1972 Int. Cl. B321) 5/12 US. Cl.161-60 7 Claims ABSTRACT OF THE DISCLOSURE A continuous filamentpolyester tow band produced from a plurality of subtows andcharacterized by a limited and controlled degree of intermingling offilaments.

This application is a continuation of copending application Ser. No.700,960, filed Jan. 26, 1968, now abandoned which is a divisionalapplication of copending application Ser. No. 382,328, filed July 13,1964, now Pat. No. 3,380,131 which relates to tows of filamentarymaterial and relates more particularly to the production of crimped towsof polyester filaments.

Man-made fibers which are to be cut into staple fiber length are oftensupplied as tows which are bundles of generally parallel continuousfilaments, each such bundle containing a large number of such filaments,generally well over 500, e.g., 6,000 to 500,000. I11 one process for themanufacture of tows, suitable for use in making staple fibers, a numberof sub-tows, each containing only a fraction of the filaments desired inthe-main tow, are first fed side-by-side to a draw frame where they arestretched, in a manner well known to the art (as discussed for examplein Man-Made Textile Encyclopedia, edited by I. J. Press, pub. 1959 byTextile Book Publishers, 1110., pages 75 and 76), to develop the desiredphysical properties (e.g. high tenacity and stiffness); the resultingdrawn tow is then fed to a crimping device, preferably a stuifercrimper, after which the crimp is set, as by feeding the band of crimpedtow, in untensioned condition, onto a belt which transports it'continuously through an oven maintained at a temperature sufficientlyhigh to set the crimp permanently but not high enough to damage or meltthe filaments. The crimped tow may then be cut into staple, baled andthen opened and spun into sliver and then into yarn, as is now mostcommonly done, or it may be fed to a device such as '21 Turbo Stapler(US. 2,748,426) or a Pacific Converter (US. 2,438,469) for directconversion into a sliver of discontinuous filaments.

It is an objectof this invention to provide a crimped tow whichprocesses especially well during its direct conversion to sliver.

Other aspects of this invention will be apparent from the followingdetailed description and claims. In this description and claims allproportions are by weight unless otherwise indicated.

In accordance with one aspect of this invention, a plurality ofundrawnsub-tows are fed to a drawing zone and, while in the form of a band insaid gene and under the drawing tension, are passed over a deflectingsurface inclined to the direct draw path of said band so that thedeflection from said direct draw path varies along the width of saidband. The use of this process makes it possible to produce novel tows inwhich the degree of intermingling of the filaments is controlled and isrelatively uniform across the width of the tow. Thus there can beproduced tows with a limited degree of intermingling which performespecially Well during direct conversion on the Turbo Stapler, producinga sliver which is uniform and has very few neps or entanglements whichmust be combed out. Such a tow can also be readily opened andderegistered on a patterned roll device of the type described inCanadian Patent No. 674,101 and can then be spread to form a Wideuniform band by passing it through an air spreader, or series of airSpreaders, in which a band of opened tow is passed through a confinedzone while air is blown against one or both of the flat sides of theband.

In contrast, when the blending of the subtows is accomplished by layingone subtow on top of another, the resulting tow (after crimping)appears, when processed on the aforesaid patterned roll device, to bemade up of distinguishable sublayers and the degree of interminglingacross the width of the tow is so great that the processed tow is notsignificantly opened by the patterned roll device and is no spreadableon the air spreader.

In addition, the tows of this invention process exceptionally well onthe Pacific Converter, particularly after they have been opened with thethreaded patterned roll device previously mentioned. In fact, thesetows, when so opened produce excellent slivers and yarns even when thePacific Converter is set to cut the filaments to very short lengths.

One aspect of this invention is illustrated in the drawing in which FIG.1 is a diagrammatic side view of an embodiment of the process for makinga package of crimped tow,

FIG. 2 is a plan view of the tow band in the drawing zone,

FIG. 3 is a view showing the cross-section of the tow band as it passesover the deflecting surfaces,

FIG. 4 is a plan view, of a different embodiment, showing two tow bandsin the drawing zone,

FIG. 5 is a schematic view of a tow opening and spreading procedure. I

As shown in FIG. 1 of the drawing, a plurality of undrawn subtows 1 aretaken from loose packages, each subtow being passed through its ownaperture in a multiapertured guideboard 2 and then to a series of smoothparallel stationary tension bars 3, each of which is preferably acircular cylinder. In passing around the second tension bar 3b the towdips into an aqueous bath 4, preferably a very dilute solution ordispersion (e.g. of about 1% concentration) of a finishing agent, suchas a lubricating and antistatic agent, in water. The wet tow passes fromthe tension bars 3 to a set of driven feed rolls 6 and then through aheated draw Zone 7 to a set of driven draw rolls 8, 8a, 8b, all of thedraw rolls being driven at a peripheral speed appreciably greater thanthat of the feed rolls 6. Each successive draw roll is preferably ofslightly larger diameter (e.g. 0.05% larger) than the draw rollpreviously engaged by the tow so that although the draw rolls are alldriven at the same rotational speed, the peripheral speed of theserolls, and the tow speed, increase as the tow moves over the draw rolls;

the peripheral speeds of the feed rolls are similarly increased along,the path of the tow.

of the filaments of each of these multifilarnent subtows are in directcontact with said bar, the tension on the subtows engenders forcesnormal to the surfaces of the' tension bars and feed rolls, which forcesurge all the filaments of said subtows towards said surfaces, thusspreading the subtows until their outer filaments are in contact .oreven slightly overlapped. The tow leaving the feed rolls thus has theappearance of a unitary band.

In the embodiment shown in FIGS. 1 and 3 of the drawing, the deflectingsurface which engages the band of tow between the feed rolls and thedraw rolls is that of a double frustoconical roll 9 mounted for freerotation on an axis generally transverse to the path of the tow,preferably on an axis lying horizontally in a vertical planeperpendicular to the direction of movement of the tow. The top of thecrotch 11 of the deflector roll 9 is slightly above the direct draw path(which direct path, in the embodiment shown in the drawing, runsstraight from the bottom of the last feed roll 6b to the bottom of thefirst draw roll 8) while the upper shoulders 12 and 13 of the deflectorroll 9 are obviously still further displaced from said direct path. Thedeflector roll 9 is so mounted that its crotch 11 is in the verticalplane of the center of the moving tow band. It will be seen that,because of the tension on the tow band and the position of the deflectorroll 9 in relation to the tow hand, those filaments which are spacedfrom the surface of said roll and which are thereby not restrained bycontact with said surface will tend to move relative to filaments atsaid surface as the tow passes over the deflector roll, as shown by thearrows in FIG. 2. By adjusting the position of the axis of the deflectorroll 9 upwards or downwards, the tendency of the filaments tointermingle can be increased or decreased, respectively, as desired; inthis manner the degree of cohesiveness of the resulting crimped drawntow can be controlled, as desired. The degree of cohesiveness can alsobe increased or decreased by using deflecting surfaces of greater orlesser inclination to the direct tow path. As shown in the drawing theincluded angle at the crotch 11 is about 60; suitably this angle may bein the range of about 30-150", preferably within the range of 45-90.Despite the fact that the filaments at the outer edges of the tow bandare drawn through a longer path, by virtue of their passage over thedeflector roll shoulders, than those at the center of the band, it isfound that the filaments are relatively uniformly drawn throughout theband.

The tow passes from the draw rolls to a dancer roll arrangement 16 andover a guide 17 to the nip of a pair of positively driven delivery rolls18 of a stuffer crimper 19 comprising a main body 21 which forms aV-shaped stuffing chamber, rectangular in horizontal cross-section,whose width is about the same as that of the tow band and whose depth(perpendicular to said width) is about 1% inches at the top, taperingdownwardly over its length of about inches. The outlet of the stuffingchamber is resiliently closed by a pivoted flapper 22, biased to closedposition in a manner well known to the art. The crimped band of towleaving the stuffing chamber, still moist at this stage, is passedthrough a distributor 23 which may be of the usual type comprising apivoted tube, generally of suflicient width to accommodate said bandwithout folding, which is swung back and forth about its pivot 24 by anysuitable mechanism to deposit the tow in a sinuous path across the widthof a driven endless belt 26 which carries the tow, resting thereon insubstantially tensionless condition, through an oven 27 which isdesirably maintained at a temperature sufficiently high to set the crimpin the filaments of the tow, eg a temperature in the range of about 85to 180 C. After passing through the oven the belt carries the tow somedistance through ambient air, whereafter the tow is distributed (as bydistributor 28) back and forth and side-to-side in a carton 29 and isthen compressed in said carton.

The preferred tow of this invention is a band of substantially parallelcrimped drawn glycol terephthalate polyester continuous filaments oftenacity greater than 2 grams per denier, the crimps of adjacentfilaments being in registry so that there are ridges, extending acrossthe tow, formed from the crests and valleys of the crimps of adjacentfilaments, said filaments having portions crossing over adjacentfilaments at small angles of less than 1 to the general direction ofsaid filaments, the filament density and degree of such crossing overbeing substantially uniform across the width of tow band, said band,after the crimps have been deregistered without further intermingling ofthe filaments, being readily spreadable laterally by a confined airstream to form a uniform web of a width at least six times the width ofsaid band. Preferably the band is cohesive and non-delaminablethroughout its thickness; i.e. it does not readily separate into layerswithout substantial filament breakage.

The following examples are given to illustrate the practice of thisinvention further.

EXAMPLE I 7 undrawn subtows, each containing 3,530 filaments ofpolyethylene terephthalate of 23 denier per filament, were fed withtheir centerlines spaced /2 inch apart to the tension bars of anapparatus as shown in 'FIGS. 1 and 2. In the drawing zone the tow bandwas subjected to an atmosphere of a hot fluid, preferably steam. Thedraw ratio was about 4.611. The tow band leaving the last feed roll was5 inches wide. The filaments necked down, under the drawing tension, ata point within the heated draw zone near the last feed roll 6b. Thedeflector roll, whose surface was of smooth metal, had a crotch 1 /2inches in diameter and shoulders which sloped toward the crotch at anangle of 60 to the axis of said roll, forming a 60 notch. The horizontaldirect draw path joining the bottom of the last feed roll and the bottomof the first draw roll was 8 feet long, and the uppermost part of thecrotch of the delivery roll was located 4 inch above this direct path,16 inches forward of the axis of the first draw roll. The drawn tow, atits zone of contact with the deflector roll, was inch wide, measuredhorizontally; at the surface of the first draw roll it formed a band 1inch wide, so that the total denier per inch of width was 128,000. Atthe deflector roll the outer edges of the tow band were about inchthick, measured perpendicular to the surface of the sloping shoulder,this thickness increased gradually toward the center of the band; abovethe crotch of the deflector roll the tow band was A; inch thick,measured perpendicular to the axis of the roll. In the stuffer crimperthe tow was subjected to direct steam (supplied at 20 p.s.i.g.) and wasgiven a fine crimp of 12 crimps per inch superimposed on a coarse crimp(of much larger amplitude) of about 3 crimps per inch. The crimp was setat a temperature of C. for 20 minutes. The set tow band, when cooled,had a degree of crimp of about 60%; the percent crimp, as used herein,being where L0 is the length of any predetermined portion of the tow andLs is the average length of the filaments of said predetermined portionwhen under a tension just suflicient to remove the crimp. Its tenacitywas 4.5 grams per denier.

The set tow band could be passed directly from the oven, after cooling,through a threaded roll opener to produce a uniform deregistered towband, 8 inches wide, which could be spread easily to a width or morethan 50 inches by passing it, directly after leaving the last of thethreaded rolls, through two stages of air spreading. In each stage therewas an air spreader made up of a pair of parallel horizontal platesbetween which the tow band passed, the plates being spaced apartslightly more than the thickness of the tow band, one of the platesbeing slitted and forming a wall of plenum chamber which extended forthe full area of the slitted plate and which was connected to a sourceof air under pressure so that air was blown through the slits in thatplate in a substantially uniform manner across the whole width of themoving tow band. Between successive air spreaders the tow passed throughtight nips of rolls driven at such a speed that the tow was pulled,under slight tension, through the spreaders. Even though the resultantweb was extremely light, it was sufliciently cohesive that it would notsplit when a stream of air was blown against it by a fan, but insteadballooned out like a sail before the wind.

The tow opening and spreading procedure referred to in theabove exampleutilizes the apparatus shown in FIG. 5, in the following manner: The towband is drawn from a bale 32 through a banding jet 33 comprising acylinder 34, having a slit running lengthwise of the cylinder at itshighest point, and a curved baflle member 36 parallel to, and spaced Vinch from, the adjacent surface of said cylinder, so that the tow band31 passes between said baflle member 36 and said cylinder 34. Air underpressure is supplied to the interior of the cylinder 34 and emerges as astream, from the slit of said cylinder, against the tow band and thebaffle member 36. The tow band 31, now about 8 inches wide, passesaround stationary tensioning bars 37, 38 and then into the nip between apair of rolls 39, 41, both rubber-surfaced, driven at a peripheral speedof 60 feet per minute and then horizontally to the nip between arubber-surfaced roll 42 and a threaded steel roll 43, driven at aperipheral speed of 102 feet per minute, said threaded roll havinghelical threads of 14 turns per inch cut about inch deep into its outersurface. The tow entering the nip between rolls 42, 43 is still about 8inches wide. From these rolls it passes still in the same horizontalplane to an air spreader having a tow-receiving slot 46 which is 24inches wide and 4 inches long. The tow-receiving slot 46 is defined byan upper wall 47 and a lower wall 48 spaced A inch apart. Below thelower wall 48 is a plenum chamber 49 supplied with air under a constantpressure of 3 p.s.i.g. from a suitable source (not shown) andcommunicating with the tow-receiving slot46 through air slits 51, each0.007 inch wide at their outlet ends and tapered to said outlets at anincluded angle of 45, said slits being each inches long and soarrangedthat the end of one slit is aligned, in the direction of movement of thetow, with theend of the adjacent slit, so that air is supplied to thetow band across thefull 24-inch width of the slot 46. The slits arearranged at small angles (e.g. about 5) to the line perpendicular to.the direction of movement of the tow with the slits on opposite sidesof the median line of the spreader being mirror images.

The tow band diverges uniformly from its 8 inch width at rolls 42, 43 tothe full 24-inch width at the exit of spreader 44, the entrance of whichis located 1 foot from the nip of rolls 42, 43. The tow is pulledthrough the spreader 44 by the action of a pair of rolls 56, 57, makingan S-wrap around these rolls, that is, passing 180 around steel roll 56then passing through the nip between the rolls and then making another180 wrap around rubber-surfaced roll 57. The tow web keeps its 24-inchwidth during its travel to and around the rolls 56, 57 which are movingat a peripheral speed of 61 feet per minute.

From the lower portion of roll 57 the tow then passes to the entrance ofair spreader 58 which is located 3 feet horizontally from, and one footbelow, the entrance of air spreader 58, which is located at the samehorizontal level as the bottom of roll 57. The spreader 58 is of thesame design as spreader 44, except that its tow-receiving slot is 50inches wide, and it is operated under the same air pressure (3 p.s.i.g.)as spreader 44. The tow web spreads uniformly in its horizontal passageto spreader 58, at which it reaches its 50-inch width and then maintainsthe same Width during its passage to a pair of rolls 59, 61, driven at aperipheral speed of 59 feet per minute, which serve to pull the webthrough the spreader 58. Roll 59 is a rubber-surfaced roll while roll 61is steel-surfaced; the top of roll 59 is on a level with thetow-receiving slot of spreader 58 and with the bottom of roll 57 The towmakes an S-wrap about the rolls 59, 61, falling from the roll 61 in afreely hanging shallow catenary onto the horizontal moving surface of awide endless take up belt 63. An idler roll 64, mounted on lever arms 66pivoted at 67, extends across the full width of the tow web on belt 63.The path of the belt is 2 feet below the bottom of roll 61 while theroll 64 is mounted inches forward (in the direction of movement of thebelt) of the center of roll 61. The web 'on belt 63 has a width of 50inches.

The bottom rolls of the roll pairs are each positively driven while thetop rolls are spring pressed downward and are rotated by the movement ofthe tow passing through the nip, with no appreciable slippage.

EXAMPLE II Using the procedure and apparatus set forth in Example Ithere was produced an intermingled drawn polyethylene terephthalate towhaving a total denier of 200,000 and a denier per filament of 1 /2, acrimp frequency of 15 crimps per inch and a percent crimp of 20%. Inthis example there were used 16 subtows, the draw ratio was 3.4:1, nosteam (or other heat) was supplied during crimping, and the oventemperature was 112 C. After cooling, the tow was continuously laid intoa carton and compressed to form a bale having a density of 210 lbs. percu. ft. Bales of this tow were fed to a Turbo Stapler and thereperformed extremely efificiently, giving a sliver with very low count ofneps or entanglements.

EXAMPLE II'I .By raising the axis of the deflector roll so that itscrotch was /2 inch above the direct draw path, and keeping all otherconditions the same as set forth in Example I, the degree ofintermingling was increased. The cross-section of the tow at the crotchof the deflector roll was much more compact, being substantially anequilateral triangle, approximately A inch on each side. The tow wasvery cohesive and resisted opening and spreading; it was substantiallyuniformly intermingled throughout its thickness and showed no signs ofseparation into sublayers.

In the embodiment shown in FIG. 4, two spaced tow bands are separatelydeflected on the deflector roll 9 which is, in that embodiment, mountedwith its axis and the upper part of its crotch below the direct drawpath so that the two tow bands do not tend to converge at the crotch.Here the intermingling takes place, as in the embodiment shown in FIG.2, by movement of filaments in a direction towards the crotch, butwithout intermingling at the crotch which occurs in the embodiment shownin FIG. 2.

It will be understood that the arrangements shown in the drawings areillustrative and may be varied as desired. Thus, the deflector roll maybe placed above the tow so that the tow passing over the deflectingsurface is below the axis of the deflector roll; or the tow path fromfeed roll to draw roll may be generally vertical or inclined, with thedeflector roll placed on either side of that tow path. A plurality ofdeflector surfaces successively engaged by the tow band may be used, andthe inclination of the deflector surfaces may vary across the width ofthe band, e.g. by using surfaces which present a curved, rather thanstraight, line to the tow. In place of a freely rotatable deflector rolla stationary surface over which the tow slides may be employed. Thus,the roll may be stationary or it may be replaced by a V-shaped deflectorbar which presents a similar surface to the tow band. Similarly, inplace of the deflector arrangement shown in FIGS. 2 and 4, a pair ofinclined deflector bars may be used; these may be both inclined in thesame direction or oppositely inclined and both need not, of course, bein the same plane. By suitably increasing the number of deflectorsurfaces, a number of tows may be processed, separately and in parallel,on a single draw frame.

It is advantageous to increase the Wear resistance and slip propertiesof the deflector surfaces by a flame-spraying procedure such asdescribed in US. Pat. 2,714,563. By the flame-spraying technique, amaterial such as aluminum oxide, chromic oxide, titanium oxide, and thelike is heated in a molten state and sprayed upon the metallic deflectorsurface in the form of fine globules which are thereby bonded to themetallic surface which may be of brass, stainless steel, aluminum, etc.

The invention is particularly suitable for the processing of tows ofpolyethylene terephthalate in which the weight of the drawn tow is aboveabout 40,000 denier per inch of tow width on the first draw roll and thedrawn filament denier is below 25. Advantageously, the filament denieris in the range of about 1 to 25, usually about 1 /2 to 1 8, preferablyabout 1 /2 to 8, and the number of filaments in the tow is over 1,000,e.g. about 2,500 to 300,000. The tow is advantageously given about 3 to80 crimps per inch, preferably about 5 to 20 crimps per inch. The numberof subtows used to produce a single tow in the process of this inventionmay be, advantageously, in the range of about 2 to 75 or more,advantageously 5 to 50.

The invention has been described particularly with respect to tows whosefilaments are of polyethylene terephthalate. It will be understood thatit is within the broad scope of the invention to carry it out with othertows, such as those made of other polyesters (e.g. the polyesters ofterephthalic acid and other glycols such as dirnethylol cyclohexane),polyamides (such as nylon 6 or nylon 6,6), polyacrylonitrile andcopolymers thereof, polyolefines such as isotactic polypropylene, etc.These polymers may, if desired, be of the more easily dyeable typecontaining groups, eg, SO Na or NH groups, which promote dyeability.

It is to be understood that the foregoing detailed description is givenmerely by way of illustration, and that variations may be made thereinwithout departing from the spirit of this invention.

What is claimed is:

1. A tow band comprising a single thickness of a plurality of sub-tows,all of said sub-tows being positioned side-by-side, crimped together,said tow band having a tenacity greater than 2 grams per denier,substantially parallel crimped and drawn polyester continuous filamentsof tenacity greater than 2 grams per denier, the crimps of adjacentfilaments being in registry so that there are ridges, extending acrossthe tow, formed from the crests and valleys of the crimps of adjacentfilaments, said filaments having at least some portions crossing overadjacent filaments at small angles of less than 1 to the generaldirection of said filaments to coalesce said subtows into a singleunitary tow, the filament density and degree of such crossing over beingsubstantially uniform across the width of tow band, said band, after thecrimps have been deregistered without further intermingling of thefilaments, being readily spreadable laterally by a confined air streamto form a uniform web of a width at least six times the width of saidband.

2. A tow band as set' forth in claim 1 in which the denier per filamentis about 1 to 25 and the crimp frequency is about 3 to 20 crimps perinch, said band being cohesive and non-delaminable throughout itsthickness.

3. A tow band as set forth in claim 2, said band being composed of asingle thickness of a plurality of subtows all side-by-side, crimpedtogether, said crossing portions extending from each sub-tow to theadjacent subtows.

4. The tow band of claim 1 wherein the polyester is glycol terephthalatepolyester.

5. The tow band of claim 1 wherein the tow band consists of 2,500 to300,000 filaments.

6. The tow band of claim 1 wherein the tow band comprises 2 to sub-tows.

7. The tow band of claim 1 wherein the tow band has a fine crimp ofabout 12 crimps per inch superimposed on a coarse crimp of about 3crimps per inch.

References Cited UNITED STATES PATENTS 3,016,581 1/1962 Smith 19653,145,429 8/1964 Resor l9l57 3,235,442 2/1966 Stump 161l73 3,277,53710/1966 Roeder et al 19-161 3,384,932 5/1968 Watson 19-65 WILLIAM A.POWELL, Primary Examiner US. Cl. X.R.

